A box contains $7$ red marbles, $6$ green marbles, and $9$ blue marbles. If a marble is randomly chosen, what is the probability that it is not blue?
Explanation: There are $7 + 6 + 9 = 22$ marbles in the box. There are $9$ blue marbles. That means $22 - 9 = 13$ are not blue. The probability is $ \frac{13}{22}$.